1. Field of the Invention
The present invention relates generally to an office chair and more specifically it relates to an office chair having tiltable seat and back for providing ergonomic seating positions for a user.
2. Description of the Related Art
Any discussion of the related art throughout the specification should in no way be considered as an admission that such related art is widely known or forms part of common general knowledge in the field.
With the ever-increasing use of office chairs, constant attention has been placed upon the advent of creating ergonomic seating positions for a user. One manner in which the office chair has been modified is the development of synchronous tilt control mechanisms so as to permit the simultaneous, but differential, tilting of the seat and back away from the normal upright position of the office chair. For example, the seat may tilt back a first amount or degree, while the back simultaneously tilts back a second amount or degree, with the degree that the back tilts generally being greater than the degree that the seat tilts.
In addition to the rearward tilting mechanisms, many office chairs have also been developed which enable the seat to effectively pivot forwardly from the normal upright position, for example the seat tilting downwardly in a forward direction or declining. The forward tilting movement has been especially desirable in high intensive work environments. However, the incorporation of the forward seat tilt feature with the synchronous differential tilting feature of the seat and back has created additional complications in office chairs.
For example, in office chairs where a forward seat tilt feature has been incorporated in addition to the synchronous differential rearward tilting feature of the seat and back, the synchronous differential tilting relationship between the seat and back continues to function irrespective of whether the seat and back are being tilted forwardly or rearwardly from the normal upright position. Hence, while the rearward tilting feature is satisfactory since the angle between the seat and back increases during such rearward tilting, the forward tilting feature is undesirable since the angle between the seat and back are tilted forwardly from the normal upright position, thus causing a closure of the angle between the seat and back during forward tilt which places stress upon the discs in the spine of the user and causes the user to be uncomfortable in the forward tilt position.
Another disadvantage associated with many of the known office chairs which have attempted to provide both rearward and forward tilt capabilities is the number of control lever arms or buttons which must be activated by the user in order to move the chair into a forward tilt position or rearward tilt position. The control arms and buttons can make use of the office chair confusing, difficult, and time consuming.
Another type of office chair developed to attempt to increase ergonomic seating positions is a user-weight operated feature. Such office chairs, generally without springs, have seat and back portions mechanically linked so the only way to activate back tension or seat movement is by forcing the back rearward. Other types of office chairs with springs, and having seat and back portions mechanically linked, require the user to apply forces upon the back of the chair that overcome the springs to force the back to tilt rearward. Generally, the user must utilize their legs or torso as a weight leverage force to overcome the springs of the office chair and provide the reclining action. In such constructions of office chairs, the difficulty of reclining the office chair generally increases the further the chair is reclined or rearwardly tilted. As made obvious, the rearwardly tilting movement of the chair can be increasingly difficult to control for lightweight and also for heavy users.
Because of the inherent problems with the related art, there is a need for a new and improved office chair having tiltable seat and back for providing an ergonomic forward or rearward tilting movement.